Hmmm...Osana from Yandere Simulator.
Asuka Langley Soryu from Evangelion. The first ever episode I watched of that old anime was where she makes her debut.
First one I can remember would be...um...probably Louise from The Familiar of Zero. Never actually saw the anime or read the manga, I just saw clips of it on Youtube with phrases like "Headshot!" and "Monster Kill!" from one of the Quake games edited in. You know what I'm talking about?